There has been a long tradition, particularly with respect to warfare, of hiding a person(s) and/or equipment so that the person(s) and/or equipment blend visually into their natural surroundings. The term typically usually used to describe this process is camouflaging. In the context of warfare, camouflage makes it difficult for troops to detect offensive threats to them and/or to identify prospective targets (e.g., artillery, aircraft or land forces) to attack using any of a number of available means. If the attacking forces or other threats (e.g., armored vehicles) can remain hidden because of the camouflaging, this gives the attacking forces or other threats a great, and dangerous, advantage.
This camouflaging process is often done by covering the object (i.e., person or equipment) to be camouflaged with a material that is designed to match the color, lightness/darkness (value) and/or pattern of the surrounding area. For example, to hide a person in a forested area, the person would be covered with a material that matches the green and brown colors of the surround foliage and branches. Traditionally, the materials used for camouflaging have been designed to merge with their surrounding background when seen by a human eye with light in the visible range: approximately 400 to 700 nm.
The military has made increasing use of electro-optical devices of various types to improve its ability to maintain visual awareness of the battlefield in conditions where the ability to observe with the human eye is degraded, such as at night or when agents (e.g., smoke) obscure vision. The increasing use of electro-optic devices such as night vision and thermal sights, that can see outside the visible light range into the infrared or ultraviolet, has consequently lead to camouflage becoming more sophisticated. Modern camouflage materials generally can mimic their surroundings when seen in the visible light range, and also in the IR and/or UV range.
For example, night vision devices in addition to being sensitive to visible light, are typically also sensitive to near-infrared light out to about 900 nm. Most living plant leaves found in forests are highly reflective in the near IR range, even if they appear dark green in the visible light range. In order to mimic this forest environment, modern forest camouflage material is made to not only match the color of green leaves in the visible range, but also to be highly reflective in the near IR range. In this way, the camouflage material will match the surrounding foliage when seen with a night vision device, i.e., both will appear as a similar light value in the display of the night vision device.
When trying to protect fixed sites, other electro-optical devices may be used to try to detect offensive forces or enemy troops or other threats. Such other electro-optical devices can include surveillance video cameras, both black & white and color. Again, if an electro-optical device has a full-color output, such as CCD camera or a color night vision device, a well-designed modern camouflage material may still match its natural background both when seen by visible light, or the combination of visible and UV and/or IR light.
The existing methods of detecting camouflaged personnel and equipment generally involve training and deploying troops using magnified optics such as binoculars and spotting scopes to slowly and closely visually examine an area such as the area surrounding a fixed site (e.g., an air base). In view of the many challenges posed, such as the size of a perimeter to be protected and the effectiveness of modern camouflage materials and techniques, it is difficult to visually scan an area and detect hidden offensive forces and/or camouflaged equipment. In addition to magnified optics, electro-optical viewing devices that see into the thermal range (e.g., in the range of 8 to 10 micron) are used to detect thermal emissions from the area being viewed, however, such thermal sights are susceptible to being fooled by well-designed thermal camouflage. Furthermore, such thermal sights are very expensive.
In addition, there are cases where the object is not camouflaged but rather the color of the object blends to a certain degree with the background in the visual light spectrum. Thus, police and search agencies as well as the military are unable to easily locate these objects even though the object was not specifically camouflaged for purposes of hiding the object in the background such as a forest. For example, a missing vehicle such as a car or truck sought by the police or non-camouflaged military vehicles could be driven into a densely packed area of trees or brush where the color of the vehicle (e.g., a green color) is such that it blends to some degree with the surrounding foliage making the vehicle difficult to see with the naked eye. In addition, the vehicle color also may contain pigments that would make the vehicle have approximately the same reflectivity of the surrounding foliage in the near IR so that the vehicle would appear to be part of the foliage.
It thus would be desirable to provide a new device for detecting the presence of objects including camouflaged objects (e.g., personnel or equipment) and new methods for detecting such objects. It would be particularly desirable to provide such a device and method whereby the object can be visually separated from its surroundings or background. It also would be particularly desirable to provide such a device and method whereby such visual separation from the background can be achieved using devices that would be simple in construction and less costly than prior art devices and such methods would not require highly skilled users to utilize the device.